docs build failed in `google-cloud-network-management`

[parthea]

See https://github.com/googleapis/googleapis/blob/42231337d84e862d417b6d3fd6af50ba0fcf932c/google/cloud/networkmanagement/v1/connectivity_test.proto#L204-L206 where there is a list which is not formatted correctly.

This caused the docs build to fail with

sphinx.errors.SphinxWarning: /usr/local/google/home/partheniou/git/google-cloud-python/packages/google-cloud-network-management/google/cloud/network_management_v1/types/connectivity_test.py:docstring of google.cloud.network_management_v1.types.connectivity_test.Endpoint:38:Block quote ends without a blank line; unexpected unindent.

Warning, treated as error:
/usr/local/google/home/partheniou/git/google-cloud-python/packages/google-cloud-network-management/google/cloud/network_management_v1/types/connectivity_test.py:docstring of google.cloud.network_management_v1.types.connectivity_test.Endpoint:38:Block quote ends without a blank line; unexpected unindent.

Instead of

  // services to provide forwarding information in the control plane. Format:
  //  projects/{project}/global/forwardingRules/{id} or
  //  projects/{project}/regions/{region}/forwardingRules/{id}

It should be

  // services to provide forwarding information in the control plane. Format:
  //
  // - projects/{project}/global/forwardingRules/{id} or
  // - projects/{project}/regions/{region}/forwardingRules/{id}

See https://github.com/googleapis/google-cloud-python/actions/runs/7128004971/job/19409110301?pr=12079

We should add a linter rule to check for incorrect formatting of lists in proto comments via https://github.com/googleapis/api-linter .